[radiowave]

There are circumstances where varying the closed-loop temperature might be useful. (Of course I have no idea whether this applies to the article.) In my system you get better efficiency by operating at lower temperatures (more of the heat in the flue gas can be extracted), but this (along with radiator surface area) limits the total rate at which heat can be transfered into the rooms. If you're allowing the house to get cold during the day when no one's in, having the water temperature at its most efficient setting might mean it takes several hours to warm the house back up. So it might be preferable to briefly run the system at a higher water temperature to more rapidly bring the room temperature up, then back off the water temperature to allow more efficient operation.